In the last decade, there has been a tremendous increase in the popularity and widespread use of mobile devices. Although mobile devices and PDAs support touch sensitive screens that are naturally suited for handwritten input, keypads continue to be the primary input interface. Current handwriting recognition technologies are not yet reliable enough for most users. Text recognition is particularly lacking for written languages with complex character sets.
More recently, the use of digital ink, which is the storing of raw handwritten data directly without performing text recognition, has been gaining in popularity. Use of digital ink opens the possibility of forgoing the need for text recognition altogether and simply operating and accessing stored handwritten notes in their raw format. The usability of handwritten digital ink documents written in can be greatly increased if previously handwritten documents can be searched.